Evaluation of different larval substrates on selected parameters of african palm weevil (Rhynchophorus phoenicis) (F.) (Coleoptera: Curculionidae)

Abstract

Proteins and carbohydrate contents of a substrate are two important macronutrients that gives organisms the energy and necessary amino acids that affect their fertility, growth, and development. However, it is often assumed that larval food stress reduces lifetime fitness regardless of the conditions. It is imperative to understand how substrates affects R. phoenicis larval development and adult reproductive performance. To mitigate these challenges that hinder the development and reproductive performance, three different diets were evaluated to assess the effect of different larval substrates on some parameters of Rhynchophorus phoenicis. Larvae were reared on diet A (500 g of rice husk, coconut coir, mango waste and water), B (500 g of rice husk, coconut coir, cocoa pod, and water), and C (500 g of rice husk, coconut coir, palm yolk, and water) and subsequent life history parameters were assessed. Cocooning rate, cocooning duration, and percentage of male and female adults were also evaluated. The emerged adults were sexed based on the presence of a setae on the male’s rostrum which are absent on the female’s rostrum The larval development on the different diets indicated a steady increase in weight gain from day 3 to day 21. The weight gain of the larvae declined after day 24. Survival rate of the larvae was significantly different (P < 0.05) among the substrates with diet C recording 78%. Cocooning and emergence rate were significantly different (P < 0.05) among the substrates. Percentage of male and female adults varied significantly (P < 0.05) among the different diets. Adult that emerged from diet C had a higher fecundity than those that emerged from the other substrates. It is therefore recommended that diets with similar characteristics of the natural host plant (oil palm yolk) should be adopted for the production of R. phoenicis larvae.